Effect of Alkyl Group on the Photocrosslinking of Alkyl Methacrylate Based Copolymers

Abstract

Three series of alkyl methacrylate based copolymers having photo-reactive side chains (C=C double bond) were synthesized and examined their performances as photopolymer in the presence of suitable oxime ester or triazine type radical photo-initiators for 365 nm light. Along to our previous report showed that correlation was observed between photochemical reactivity and chain length of the side chain/density of reactive side chain in the cyclohexyl methacrylate main chain. Our proposed mechanism is that sterically stacked nonpolar cyclohexyl groups may push out the polar reactive side chains, and length and density of the side chain controls cross linking between two reactive sites in the single main chain or two different main chains. Now we have examined structural effect of the alkyl groups on the efficiency of photocrosslinking. We have examined 5 series and totally 15 polymers. As a result, cyclohexyl methacrylate based copolymer showed excellent performance for polymerization.

Nanocapsules for 5-fluorouracil delivery decorated with a poly(2-ethylhexyl methacrylate-co-7-(4-trifluoromethyl)coumarin acrylamide) cross-linked wall

“…The dispersion was extruded (30 times) at 35 1C through a polycarbonate nucleopore track-etch membrane (Whatman, with a 0.2 mm pore size) using a Lipex stainless steel extruder (Northern Lipids). The photocrosslinking of the alkyl methacrylate copolymer 54 was obtained in the presence of the radical photo-initiator (DMPA) for UV l = 350 nm light to induce polymerization, the sample was irradiated for 5 hours with UV light (l = 350 nm) in a quartz tube in a photochemical reactor (Rayonet RPR-200, Southern New England, USA) equipped with a stirrer and 16 lamps (the energy was approximately 400 W, and the temperature inside the reaction chamber varied between 35 1C and 40 1C). First, irradiation was carried out with 350 nm of light (14.4 mW cm À2 ) for an appropriate period of time to yield the cross-linked version via photodimerization.…”

Improvement of the photopolymerization and bottom-curing performance of benzocarbazole oxime ester photoinitiators with red-shifted absorption

“…Actually, these photoinitiators are widely utilized in the field of photolithography using the i-line. [22][23][24][25][26] PI-3, which has a trimethylbenzoylbenzocarbazole-substituted oxime moiety as the chromophore and an acetyl group in the ester part, is a recently developed photoinitiator for advanced processing.…”

“…The species actually initiating the polymerization are phenyl radical for PI-1 and the methyl radical for PI-2. Although both phenyl and methyl radicals are highly active to initiate the generation of alkyl radicals even in a highly viscous environment such as a color or black resist, 12,24) the methyl radical has larger mobility than that of the phenyl one in the film. 24) This larger mobility of the methyl radical could contribute to higher sensitivity in PI-2.…”

“…Although both phenyl and methyl radicals are highly active to initiate the generation of alkyl radicals even in a highly viscous environment such as a color or black resist, 12,24) the methyl radical has larger mobility than that of the phenyl one in the film. 24) This larger mobility of the methyl radical could contribute to higher sensitivity in PI-2. Actually, the newly developed PI-3 also yields the methyl radical by the photochemical reaction.…”

Recent advances on carbazole-based oxime esters as photoinitiators of polymerization

“…[247] Interestingly, OXE-02 displayed an outstandingly high sensitivity in resins containing black pigments so that OXE-02 was immediately commercialized by the color filter resist manufacturers. [248][249][250][251][252][253] Noticeably, only one initiating and reactive species is formed by photodecomposition of OXE-02. Indeed, iminyl radicals formed in first step cannot undergo a further fragmentation, furnishing radicals unable to add onto acrylic double bonds.…”